Only child for 9 years

Need some advice , My husband & I have a almost 9 year old very spoiled son together. He is the only grandchild & child at the moment. We are due in June with our 2nd and very excited. We told our son he's going to be a big brother and he's happy. But at times he seems jealous like when daddy rubs my belly or if we're talking about the baby. I love my son more than anything and it's been all about him for soooo long. How can I let him know that my love won't change once the baby is here and that he is still loved and cared for by us. I don't want him feeling left out. The baby will be here for the summer and while he's on summer break, any ideas on bonding with my son and the baby or advice?? Thanks for any advice given !!!